1. Field of the Invention
The present invention relates to an actinic-ray- or radiation-sensitive resin composition, compounds and a method of forming a pattern using the composition. In particular, the present invention relates to an actinic-ray- or radiation-sensitive resin composition and compounds employed in a semiconductor production process for an IC or the like, a circuit board production process for a liquid crystal, a thermal head or the like and other photofabrication processes, and also relates to a method of forming a pattern with the use of the composition. More particularly, the present invention relates to an actinic-ray- or radiation-sensitive resin composition that is suitable when, for example, electron beams or far-ultraviolet rays of wavelength 250 nm or shorter, preferably 220 nm or shorter are used as an exposure light source, and also relates to a method of forming a pattern with the use of the composition.
In the present invention, the terms “actinic rays” and “radiation” mean, for example, brightline spectra from a mercury lamp, far ultraviolet represented by an excimer laser, extreme ultraviolet, X-rays, electron beams and the like. In the present invention, the term “light” means actinic rays or radiation.
2. Description of the Related Art
In photosensitive compositions, such as a chemical-amplification resist composition, for use in semiconductor photolithographic processing, etc., especially when an ArF excimer laser (wavelength: 193 nm) is used as a light source, it is beneficial to employ a resin having an alicyclic hydrocarbon group from the viewpoint of transparency and resistance to dry etching.
Stronger acids are demanded for the photosensitive compositions containing the resin having an alicyclic hydrocarbon group. Thus, use is made of compounds that generate perfluoroalkylsulfonic acids, such as triphenylsulfonium trifluoromethanesulfonate or the like.
However, the perfluoroalkylsulfonic acids exhibit high hydrophobicity, so that the photosensitive compositions containing the acid generators that generate these acids have poor affinity to aqueous developers. Thus, it has been likely to encounter the problems that a decrease of sensitivity is caused by deteriorated developability and development defects occur.
In this connection, patent reference 1 discloses photosensitive compositions each containing a compound that generates a specified acid containing a fluorine atom.
However, further enhancement of various performances, especially exposure latitude and line edge roughness performances, is demanded in accordance with the further enhancement of pattern fineness.
Moreover, it is pointed out that in the application of a chemical-amplification resist to liquid-immersion exposure, the resist layer is brought into contact with the immersion liquid at the time of exposure to thereby alter the properties of the resist layer, and that components negatively affecting the immersion liquid are leached from the resist layer. Patent reference 2 describes examples in which the resist performance is changed by immersing the resist for ArF exposure in water before or after the exposure, and points out that this is a problem of the liquid-immersion exposure.
Patent reference 3 describes examples in which an acid generator with a specified sulfonimide structure is used in the liquid-immersion exposure.
Meanwhile, in the application of triarylsulfonium salts, such as triphenylsulfonium salts, to an ArF excimer laser, a high sensitivity and high quantum yield can be attained. However, the application is disadvantageous in that a strong absorption attributed to the benzene ring thereof causes the transmitted light to become less as the depth from the surface of a resist film is increased, resulting in the formation of a tapered pattern configuration. Therefore, various attempts are being made with respect to the photoacid generators for highly sensitive photoresists having high transparency at a wavelength of 193 nm.
As examples of such attempts, patent reference 4 proposed using sulfonium salt compounds each having an alkoxynaphthalene skeleton. Further, patent reference 5 proposed using sulfonium cation salts each having an alkoxynaphthalene skeleton in which the counter anion consisted of a sulfonimide. However, using these compounds, although the transparency in the region of far ultraviolet was high, was unsatisfactory in the lithographic performance.